Field of the Invention
The present invention relates to an image file generating method and apparatus which is used upon recording a digital image obtained from a film or a digital camera as an image file in a recording medium such as a CD-R and an MO disc.
A digital output service has been carried out wherein a digital image read from a film is recorded in a photo CD, an MO disc or the like and provided to a customer. In the FlashPix standard proposed by Eastman Kodak Co., a structured storage file comprising a storage and a stream including image data and various kinds of property information thereof has been defined as an image file format appropriate for a digital output service regarding photographs.
A digitally output photograph is used for appreciation by displaying it on a monitor and for generating additional print afterwards. On this occasion, the resolution appropriate for printing is generally different from that appropriate for monitor display. Furthermore, in the case of a monitor, the resolution necessary for display varies depending on the size of a monitor screen. Therefore, an image file defined by the FlashPix standard has a plurality of image data sets at different resolutions.
A digital output service such as the above is often used in combination with printing service when a film is deposited for development, for example. Therefore, as a system for smoothly operating such a service, Fuji Photo Film Co. Ltd. has proposed a photograph finishing system which carries out both generation of photographic print and output in a recording medium at one-time film reading (see Japanese Unexamined Patent No. 10(1998)-73921 and U.S. Ser. No. 08/974,888). In Japanese Unexaimined Patent Publication No. 10(1998)-73921 and U.S. Ser. No. 08/974,888, a system has been described which carries out output in a recording medium by using a file format based on the FlashPix standard.
More specifically, the above photograph finishing system carries out tone processing and color processing on a digital image obtained by a film scanner or a digital camera, and outputs print of the image after enlargement or reduction of the digital image in accordance with the print size and sharpness enhancing processing or the like carried out thereon. The photograph finishing system also converts the digital image after the sharpness enhancing processing into a file format based on the FlashPix standard and records the file in a recording medium.
In the FlashPix standard, four kinds of interpolation filters are defined which generate half-resolution image data from high resolution image data. Therefore, a digital image having been obtained is generally enlarged to the print size, and sequential interpolation processing is carried out on the image for printing by using the interpolation filters of the FlashPix standard. In this manner, image data at resolutions {fraction (1/2, 1/4, 1/8)}, and {fraction (1/16)} of that of the original digital image are generated.
Quality of a digital image generally degrades by repeated enlargement or reduction processing. In other words, the smaller the number of repetition of enlargement or reduction processing, the better the quality is. However, in the above photograph finishing system, lower resolution image data are generated by repeated interpolation processing on high resolution image data generated for printing. Therefore, image data other than the ones for printing have experienced at least two times of interpolation processing.
Based on consideration of the problems described above, an object of the present invention is to provide a method and apparatus which minimizes image quality degradation due to enlargement or reduction of a digital image.
An image file generating method of the present invention generates image data for printing at a resolution appropriate for printing and image data sets at different resolutions changing stepwise and lower than the resolution of the image data for printing by using a digital image obtained by an image obtaining apparatus, and generates a structured storage file comprising the image data for printing and at least one of the image data sets at different resolutions as components of the image file. The image file generating method is characterized by that the image data for printing and at least one of the image data sets at different resolutions are generated by applying direct interpolation processing on the digital image.
The image obtaining apparatus including a cable interface and a memory card reader and the like to obtain an image from a film scanner or a digital camera. Furthermore, the image obtaining apparatus is meant to include a medium drive for reading a recording medium wherein a digital image has been recorded and communication equipment for receiving a digital image transferred via a network.
The print means high quality photographic print generated mainly by a photographic service provider. In other words, the resolution appropriate for printing means a resolution (for example, 1800xc3x971000) high enough to generate high quality photographic print.
The image data sets at stepwise changing resolutions mean a combination of image data sets having resolutions {fraction (1/2, 1/4, 1/8)}, and {fraction (1/16)} of the resolution of the digital image, for example.
The structured storage file has a hierarchy similar to a directory structure of a conventional file system. Each component composing the hierarchy can be dealt with by different kinds of application software. Since the structured storage is widely known as a technique used in the Component Object Model (COM) proposed by Microsoft Corp., detailed explanation is not provided here.
Upon interpolation processing, in the case of enlargement ratio equal to or larger than 2 or reduction ratio equal to or smaller than xc2xd, image quality cannot be maintained unless the length of an interpolation filter is extended. As a result, calculation load becomes heavy. Therefore, among the image data sets at different resolutions, image data sets at resolutions between xc2xd and 2 times the resolution of the digital image may be generated by directly interpolating the digital image, and the image data sets at resolutions other than the above may be generated by applying stepping interpolation processing on the image data sets at the resolutions within the above range.
An image file generating apparatus of the present invention generates image data for printing at a resolution appropriate for printing and image data sets at resolutions changing stepwise and lower than the resolution of the image data for printing by using a digital image obtained by an image obtaining apparatus, and generates a structured storage file comprising the image data for printing and at least one of image data sets at different resolutions as components of the image file. The image file generating apparatus comprises printing image data generating means which generates the image data for printing by directly applying interpolation processing on the digital image, stepping resolution image data set generating means which generates at least one of the image data sets at different resolutions by applying direct interpolation processing on the digital image, and file generating means which generates the structured storage file by using the image data for printing and the image data sets at different resolutions.
According to the image file generating method and apparatus of the present invention, upon generating the image data sets at different resolutions, the image data sets are generated by directly applying interpolation processing on a digital image having been obtained, rather than applying stepping interpolation processing on data of a high resolution image having been enlarged for printing. Therefore, degradation of image quality due to repeated interpolation processing can be minimized.
Among the image data sets at different resolutions, if image data sets at resolutions between xc2xd and 2 times the resolution of the digital image are generated by directly interpolating the digital image, and the image data sets at resolutions other than the above are generated by applying stepping interpolation processing on the image data sets at the resolutions within the above range, problems such as increased calculation load due to longer filter length can be avoided.